The present invention relates to a method and an apparatus for fixing an object to a support structure and, more particularly, to the secure mounting of an object to a low-strength support structure, such as a porous masonry wall or a block-like structure having interior hollow cavities.
In general, the prior art has encountered very serious difficulties when it is desired to mount an object, such as a cladding panel, onto a low-strength support structure. Because such structures are typically porous and usually have large vacant cavity areas, they have a very low resistance to fracture and thus do not provide an adequate surface for an object to be securely mounted thereon. In the case where an expansion anchor member is placed in an anchoring hole which is provided in the low-strength support structure and radially expanded, the support structure is especially subject to crumbling. It will be appreciated that when the circumferential wall of such anchoring holes are so destroyed, the clamping force which secures the object to the support structure is no longer sufficient to perform its function. Once destroyed, the anchor hole can no longer be used anymore for mounting purposes.
In porous block-like supporting structures having interior hollow cavities separated by partition walls, it is known to utilize an extra-long dowel whose length is selected so that it can engage and grip several of the partition walls in the interior of the support structure. Such oversized dowels usually have spreadable elements which are adapted to engage a large area at the rear sides of the partition walls. Thus, as a result of distributing the expansion pressure force over several partition walls, a large extraction force is required to remove an object from the support. However, even with this prior-art approach, one still subjects the interior of the structure to some crumbling. Moreover, the higher anchoring values frequently necessary to mount a heavy object on a support cannot always be achieved. Finally, not only are the spreadable elements costly to manufacture, but this approach cannot be successfully used when the support structure is relatively thin.
In other porous material structures, the prior art teaches the use of adhesives to improve the holding strength or retention of the anchoring member. However, the retention properties of the dowel are limited by the low breaking strength of the masonry material and, moreover, the adhesive technique cannot be effectively used for block-type walls having interior cavities.
It is also known in the prior art to mortar or cement dowels in place in an anchoring hole provided in masonry. Such an anchoring hole has a cross-section which is considerably larger than the cross-sectional measurement of the dowel or anchoring member. Thereupon, the anchoring hole is filled with a cement-like mixture, and then the dowel is inserted into this mixture. In order to ensure that the dowel is correctly positioned in the hole, it is however necessary to support and hold the dowel therein until the mixture sets.
This prior-art method has the drawback that it requires a considerable amount of time. It will be appreciated that, in many applications where a great plurality of these dowels are required to be installed, that the loss of time and the additional labor expenses are very considerable. Furthermore, this prior-art cementing technique cannot utilize expansion anchor devices since their leading end faces must be closed so that they can be pressed into the cement mixture.
For all of the above considerations, the only time that dowels are generally cemented into walls is in the mass-production of pre-fabricated concrete parts. In this mode of production, the dowels are positioned in place by means of spikes or pins which are pre-arranged on slabs. The pins are positioned into the respective inner passages of the dowels and thereby hold the dowels in place until the cement has hardened. This approach, as the others described above, has the disadvantage of requiring additional holding elements.
Finally, in the aforementioned parent application having Ser. No. 617,832, the applicant has proposed mounting an object to a support structure by inserting an anchor member into an anchoring hole and injecting a hardenable substance through an interior passage of the anchor member and from there to the exterior of the latter so as to fix the anchor member in the hole upon the curing of the hardenable substance.
Although this approach is generally effective in accomplishing its intended purpose, difficulties have arisen. First of all, the hardenable substance takes a long amount of time to cure properly. Thus, before mounting an object to the support structure, one is required to wait for a considerable amount of time to elapse. In addition, the interior hollow cavities of the block-like support structure have generally been completely filled with the hardenable substance. This is particularly expensive and wasteful when the the structure has very large cavities.
In order to overcome the necessity for completely filling the hollow interior cavities of the support structure, the applicant has further proposed the use of quick-setting substances which cure almost as soon as they reach the exterior of the anchor member. The rapid setting of such substances tends to partially fill a cavity. However, it has proved to be very difficult to control the amount of such curable substances required for a particular application. The high cost of such substances and the lack of any accurate prediction as to the exact amount required results in increased costs and a wastage of material.